The germinative epithelium of sheep vibrissae and wool follicles has extensive proliferative potential but is dependent on the dermal papilla

Abstract

Aim:To investigate the growth potential of keratinocytes derived from the germinative epithelium (GE) of ovine hair follicles. Stem cells from the outer root sheath (ORS) of hair follicles migrate to the GE in the lower follicle where they proliferate and differentiate to form the hair fiber. It has been suggested that the GE comprises transit-amplifying cells and that the duration of anagen is determined by their limited proliferative potential. However, we show here that keratinocytes derived from the GE of ovine follicles grow extensively in vitro, arguing against this hypothesis.Materials and Methods:Primary cultures of keratinocytes were initiated from microdissected GE tissue from ovine vibrissae and wool follicles. Clonal lines of keratinocytes were derived by limiting dilution. Their growth potential was determined by exhaustive serial passaging. Expression of differentiation markers was evaluated by real-time polymerase chain reaction.Results:Initiation of these cultures required that interaction between the GE and dermal papilla was maintained. However, the keratinocytes could subsequently be cloned and were grown as pure cell populations for 26-52 cell doublings. This proliferative potential is several orders of magnitude greater than required to maintain a single anagen phase. The keratinocytes were indistinguishable from ORS keratinocytes from the same follicles, expressing K14 while undifferentiated, and upregulating the epidermal and inner root sheath markers, loricrin and KRT27 on differentiation. Thus, these cells initially depend on papilla-derived signals to grow, but can revert to an ORS-like phenotype in vitro. Their extensive proliferative capacity shows that the GE is not an exclusively transit-amplifying cell population.

Hair-Growth-Promoting Effects of the Fish Collagen Peptide in Human Dermal Papilla Cells and C57BL/6 Mice Modulating Wnt/β-Catenin and BMP Signaling Pathways

“…Gprc5d is highly expressed in the middle and late stage of the anagen phase of the hair cycle, but not in the telogen phase [ 14 , 15 , 57 ]. Krt27 is a hair-follicle-specific epithelial keratin that is upregulated during keratinocyte differentiation and is known to be mainly involved in hair follicle morphogenesis and the hair cycle [ 15 , 16 , 58 , 59 ]. Additionally, Ki67 is a well-known marker of hair follicle proliferation and morphogenesis [ 12 ].…”

“…Gpr5cd is highly expressed in the late growth phase (anagen) but is not expressed in the resting phase (telogen) [ 14 , 15 ]. Krt27 is a hair-follicle-specific epithelial keratin that is mainly involved in hair follicle morphogenesis and is known to be upregulated during keratinocyte differentiation [ 15 , 16 ].…”